The invention relates to a drilling tool according to the preamble of claim 1. Such a drilling tool is known in principle from EP-B-0 796 161. The drilling tool consists of a parent body and cutting inserts which can be inserted into the parent body. The parent body is provided with flutes for the chip removal. These flutes can either be straight or twisted. For attaching the cutting inserts, an insert seat is provided at the end of one or more flutes. This insert seat serves as a receptacle for the cutting insert.
In the case of the above-mentioned drilling tool, the cutting insert is designed as a reversible insert. The known reversible insert has a base surface and a rake face facing away from the base surface. The reversible inserts rests with the base surface on a corresponding holding surface in the insert seat. The reversible insert has a substantially rectangular basic shape, with the result that the rake face is also substantially rectangular. In this way, the long side edges of the rake face each form a secondary cutting edge and the short side edges each form a main cutting edge. If the reversible insert rests in the insert seat, one main cutting edge and one secondary cutting edge are rendered inactive because they bear against the side walls of the insert seat, whereas the remaining active secondary cutting edge and the likewise remaining active main cutting edge project from the insert seat and thus from the tool in order to be able to machine the drill hole when the drilling tool is rotating. The active main cutting edge and the active secondary cutting edge, on the one hand, and the inactive main cutting edge and the inactive secondary cutting edge, on the other hand, in each case form a cutting edge pair belonging to one another. If the active main cutting edge and the active secondary cutting edge have become worn, the reversible insert in the insert seat is simply rotated by 180° in the plane of the insert seat, with the result that the previously active main cutting edge and the previously active secondary cutting edge are rotated into their respective inactive positions, whereas the previously inactive cutting edges now project as active cutting edges from the insert seat in the manner described. The reversible inserts provided in the known drilling tool therefore always have two usable cutting edge pairs, each formed by a secondary cutting edge and a main cutting edge.